where the name production is a gramatical production that is a case-insensitive
match for the given parameter-name. If the unparsed-string can be parsed by
the grammar in multple ways, choose the one in which name appears as close to
the beginning of the string as possible. If the unparsed-string cannot be
parsed by the grammar above, return the empty string.

Decoding the File Name

To filename-decode an encoded-string, use the following algorithm:

If the encoded-string contains non-ASCII characters, emit the encoded-string (decoded as ISO-8859-1) and abort these steps.